UV-absorbing ophthalmic lenses, in particular UV-absorbing contact lenses are typically produced in mass by a so-called cast-molding process, which involves thermo- or UV-induced free-radical polymerization of a lens-forming composition including a polymerizable UV-absorber and at least one vinylic monomer, macromer and or prepolymer in molds. Copolymerizable benzotriazole, benzophenone and triazine UV absorbers, which include an ethylenically unsaturated group covalently linked to their UV-absorbing moieties, are known and have been used previously. Those UV-absorbers can be incorporated into the polymer matrix of ophthalmic lenses. However, unpolymerized UV-absorber must be removed through extraction process to ensure obtained ophthalmic lenses to have required biocompatibility for use. In addition, when the lens production is relied on UV-induced polymerization process, which has a processing cycle shorter than that of the thermo-induced polymerization process, there are several disadvantages associated with use of a known polymerizable UV-absorber. First, the efficiency of incorporation of the UV-absorber in lenses may not be certain. Second, a UV-absorber present in a lens forming composition can reduce the amount of UV radiation available to initiate polymerization and may even lower the efficiency of covalent incorporation of the UV absorber into resultant lenses. Unreacted UV absorbers generally must be removed from the lenses in one or more extraction processes. Third, a UV-absorber may result in ineffective or uneven photo-polymerization of the lens forming composition.
Therefore, there still exists a need for a cost-effective method for making UV-absorbing contact lenses.